IMO, it shouldn't it be more than 255(max varchar) characters in anycase or hard-coded 255 is fine, why it should be configurable?

The current standard for email is that the maximum *guaranteed* email address length be 320 chars (64 chars for username, 255 for domain, 1 for '@') [1]. However, to the extent possible, SMTP servers should not limit the size of email addresses. Realizing Django isn't an email server framework, having it provide a reasonable default (75 is arbitrary but backwards compatible) isn't ridiculous, but this patch should let users override the default. Any further discussion should probably be brought back up on the dev mailing list.

The consensus from on the django-dev thread was at least two maintainers were against making it configurable. So I don't there's enough consensus here yet that it's ready-for-checkin. There are some arguments for making it configurable and similar ones against, but we should go through the process.